U.S. patent application number 10/799085 was filed with the patent office on 2005-09-15 for wellhead and control stack pressure test plug tool.
Invention is credited to Dallas, L. Murray, McGuire, Bob.
Application Number | 20050199389 10/799085 |
Document ID | / |
Family ID | 34920430 |
Filed Date | 2005-09-15 |
United States Patent
Application |
20050199389 |
Kind Code |
A1 |
Dallas, L. Murray ; et
al. |
September 15, 2005 |
Wellhead and control stack pressure test plug tool
Abstract
A test plug tool for use in testing a pressure integrity of a
pressure control stack mounted to a wellhead, including a joint
between a casing and a casing support in the wellhead. The test
plug tool includes a test plug of an appropriate diameter used to
pressure test the pressure control stack as well as a joint between
any one of a surface casing and the wellhead, an intermediate
casing and an intermediate casing mandrel, and a production casing
and a production casing mandrel. The pressure integrity of the
wellhead is ensured at each stage of well drilling and well
completion, and safety is improved. Optionally, a backpressure
valve permits pressurized fluid that leaks below the test plug tool
to flow upwardly through a central bore in a landing tool that is
secured to the test plug tool to permit detection of the leak.
Inventors: |
Dallas, L. Murray;
(Fairview, TX) ; McGuire, Bob; (Oklahoma City,
OK) |
Correspondence
Address: |
NELSON MULLINS RILEY & SCARBOROUGH, LLP
1320 MAIN STREET, 17TH FLOOR
COLUMBIA
SC
29201
US
|
Family ID: |
34920430 |
Appl. No.: |
10/799085 |
Filed: |
March 12, 2004 |
Current U.S.
Class: |
166/250.07 |
Current CPC
Class: |
E21B 47/117
20200501 |
Class at
Publication: |
166/250.07 |
International
Class: |
E21B 047/00 |
Claims
We claim:
1. A test plug tool for use in testing a pressure integrity of a
pressure control stack mounted to a wellhead, including testing the
pressure integrity of a joint between a casing and a casing support
that secures the casing to the wellhead stack assembly, the test
plug tool providing a high pressure seal with the casing below the
joint between the casing and the casing support.
2. The test plug tool as claimed in claim 1 further comprising a
test plug hanger and a test plug, the test plug hanger including a
hanger flange at a top end thereof and a test plug support leg that
depends from the hanger flange and includes a bottom end for
supporting the test plug in the casing.
3. The test plug tool as claimed in claim 1 further comprising a
fluid passage that permits pressurized fluid injected into the
wellhead stack assembly to flow through the hanger flange.
4. The test plug tool as claimed in claim 2 wherein the test plug
comprises a cup tool.
5. The test plug tool as claimed in claim 4 wherein the cup tool
comprises a cup sleeve that terminates in a bullnose for guiding
the test plug through the wellhead stack assembly.
6. The test plug tool as claimed in claim 4 wherein the cup tool
comprises an elastomeric cup for sealing against the casing, an
annular sealing element compressed against the casing by the
elastomeric cup, and a gauge ring to inhibit the sealing element
from being extruded into an annulus between the bullnose and the
casing.
7. The test plug tool as claimed in claim 2 wherein the test plug
leg is hollow to reduce a weight of the test plug tool.
8. The test plug tool as claimed in claim 2 further comprising a
landing joint connector located above the hanger flange.
9. The test plug tool as claimed in claim 8 wherein the landing
joint connector comprises a socket with a box thread for receiving
a pin thread of one of a drill pipe, a production tubing, and a
landing joint.
10. The test plug as claimed in claim 2 wherein the hanger flange
is received in a top end of a drilling flange and has beveled top
corners engaged by locking pins of the drilling flange to lock the
test plug tool in the wellhead stack assembly.
11. The test plug tool as claimed in claim 5 wherein the cup sleeve
is a hollow cylinder.
12. The test plug tool as claimed in claim 2 wherein the test plug
tool is used to pressure test a joint between a production casing
and a production casing mandrel of the wellhead stack assembly, and
the test plug hanger comprises an elongated tubular member having a
pin threaded top end for treaded engagement with a flanged adapter
for sealing a top of the wellhead stack assembly, and a hanger
flange having a beveled bottom shoulder received in a bowl-shaped
abutment at a bottom of a tubing head spool of the wellhead stack
assembly.
13. The test plug tool as claimed in claim 12 wherein the test plug
hanger further includes a fluid passage through a sidewall of the
test plug hanger, the fluid passage being located below the hanger
flange and above a bottom end of the test plug hanger.
14. The test plug tool as claimed in claim 13 wherein the test plug
comprises a cup tool.
15. The test plug tool as claimed in claim 14 wherein the cup tool
comprises a cup sleeve that terminates in a bullnose for guiding
the test plug through the wellhead stack assembly.
16. The test plug tool as claimed in claim 14 wherein the cup tool
comprises an elastomeric cup for sealing against the casing, an
annular sealing element compressed against the casing by the
elastomeric cup, and a gauge ring to inhibit the sealing element
from being extruded into an annulus between the bullnose and the
casing.
17. The test plug tool as claimed in claim 2 wherein the test plug
hanger comprises: an axial passageway bored through a central
portion of the test plug hanger, the axial passageway permitting
pressurized fluid that may have leaked below the test plug to flow
upwardly through the central portion of the test plug hanger; and a
backpressure valve in fluid communication with the axial
passageway, the backpressure valve throttling the pressurized fluid
flowing upwardly through the test plug hanger.
18. The test plug tool as claimed in claim 17 further comprising a
landing tool connected to an upper portion of the test plug hanger,
the landing tool defining a central bore through which pressurized
fluid can flow upwardly after being throttled through the
backpressure valve.
19. The test plug tool as claimed in claim 18 wherein the
backpressure valve is threadedly connected to an upper portion of
the test plug hanger.
20. The test plug tool as claimed in claim 19 wherein the
backpressure valve comprises a spring-loaded ball valve having a
spring exerting a downward force on a ball for obstructing an
aperture of the backpressure valve.
21. The test plug tool as claimed in claim 20 wherein the
backpressure valve further comprises an annular body having a lower
annular shoulder defining the lower aperture, the lower annular
shoulder supporting a gasket against which the ball is forced by
the spring.
22. The test plug tool as claimed in claim 21 wherein the test plug
hanger has an annular groove for housing a seal for providing a
fluid-tight seal between the backpressure valve and the test plug
hanger.
23. A method for testing a pressure integrity of a pressure control
stack mounted to a wellhead, comprising: inserting a test plug into
the wellhead stack assembly and testing the pressure integrity of a
joint between a casing and a casing support that secures the casing
to the wellhead stack assembly using the test plug tool, which
provides a high pressure seal with the casing below the joint
between the casing and the casing support.
24. The method as claimed in claim 23, further comprising:
inserting the test plug tool using a landing tool; landing the test
plug in the casing beneath the joint between the casing and the
casing support; locking the test plug tool in the position in which
the test plug is beneath the joint between the casing and the
casing support; detaching the landing tool from the test plug tool;
retracting the landing tool from the wellhead stack assembly;
pressurizing the wellhead stack assembly to at least an estimated
operating pressure; and inspecting the seals and joints of the
wellhead stack assembly, including the joint between the casing and
the casing support, to determine whether the seals and joints have
withstood the test pressure.
25. The method as claimed in claim 24 further comprising pressure
testing a joint between a surface casing and a wellhead.
26. The method as claimed in claim 24 further comprising pressure
testing a joint between an intermediate casing and an intermediate
casing mandrel.
27. The method as claimed in claim 24 further comprising pressure
testing a joint between a production casing and a production casing
mandrel.
28. The method as claimed in claim 24 further comprising a step of
inserting the test plug tool through a blowout preventer mounted to
the wellhead stack assembly and pressure testing the rams of the
blowout preventer as well as the wellhead stack assembly.
29. The method as claimed in claim 24 further comprising steps of,
subsequent to locking the test plug tool but prior to detaching the
landing tool: pressurizing the wellhead stack assembly; and flowing
pressurized fluid that may have leaked below the test plug tool
upwardly through an axial passageway in the test plug tool;
throttling the pressurized fluid through a backpressure valve
selectively obstructing the axial passageway; and flowing the
pressurized fluid upwardly through a central bore of the landing
tool for alerting a user of a leak in the test plug tool.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is the first application filed for the invention.
MICROFICHE APPENDIX
[0002] Not Applicable.
TECHNICAL FIELD
[0003] The invention relates generally to pressure-testing tools
for pressure control stacks on wellheads and, in particular, to
test plug tools for pressure-testing of those control stacks.
BACKGROUND OF THE INVENTION
[0004] Prior art pressure-test plug tools for testing the pressure
integrity of pressure control stacks on wellheads are well known in
the art. The pressure-test plug tools are used to test the pressure
integrity of control stack components such as blowout preventers,
valves, tees, etc., and joints between the components prior to
drilling or stimulating a well.
[0005] While most prior art test plug tools are known to function
well, they all suffer from a drawback in that they are only
designed to test the pressure integrity of the stack above a casing
joint, i.e., above a connection between a casing and a casing
support. With prior-art devices, the pressure integrity of the
casing joint cannot be verified. During well stimulation
operations, where fluid pressures may spike to 20,000 PSI, this
joint may be susceptible to leakage and/or failure, resulting in
expensive repairs, cleanup, downtime and potential environmental
damage.
[0006] Many configurations for pressure-test plug tools have been
invented; For example, in U.S. Pat. No. 5,775,422 (Wong et al.)
entitled TREE TEST PLUG, the test plug is lodged within the tubing
hanger, i.e., above the connection between the surface casing and
the wellhead. In this configuration, the pressure integrity of the
stack beneath the tubing hanger cannot be verified.
[0007] In U.S. Pat. No. 4,121,660 (Koleilat) entitled WELL PRESSURE
TEST PLUG, the test plug is seated in the bore of the wellhead.
With the test plug in this configuration, the pressure integrity of
the wellhead-to-casing joint cannot be tested.
[0008] Similarly, in U.S. Pat. No. 4,018,276 (Bode) entitled
BLOWOUT PREVENTER TESTING APPARATUS, the test plug is positioned in
the bore of the wellhead. The position of the test plug permits
pressure-testing of the blowout preventer but does not permit
pressure-testing of the wellhead or the casing connection.
[0009] Likewise, in U.S. Pat. No. 3,897,824 (Fisher) entitled
BLOWOUT PREVENTER TESTING APPARATUS, the test plug is positioned in
the bore of the wellhead beneath the blowout preventer. With the
test plug in this location, it is not possible to verify the
pressure integrity of the lower part of the wellhead, such as the
joint between the wellhead and the well casing.
[0010] In U.S. Pat. No. 3,177,703 (Waters et al.) entitled METHOD
AND APPARATUS FOR RUNNING AND TESTING AN ASSEMBLY FOR SEALING
BETWEEN CONDUITS, the test plug is positioned in the bore of the
wellhead above the joint between the wellhead and the casing. With
the test plug in this location, it is not possible to pressure-test
the wellhead-casing joint.
[0011] In U.S. Pat. No. 2,951,363 (Diodene) entitled TOOL FOR
TESTING WELL HEAD EQUIPMENT, the test plug is also positioned above
the wellhead and casing joint. Pressure-testing of the casing joint
is not possible with the test plug located in that position.
[0012] There therefore exists a need for a test plug tool for
pressure-testing wellhead control stacks that permits testing of
the pressure integrity of a casing joint, i.e., the joint between a
surface casing and a wellhead, the joint between an intermediate
casing and an intermediate casing mandrel, or the joint between a
production casing and a production casing mandrel.
SUMMARY OF THE INVENTION
[0013] It is therefore an object of the invention to provide a test
plug tool for use in testing the pressure integrity of a pressure
control stack mounted to a wellhead, together defining a wellhead
stack assembly, including testing the pressure integrity of a joint
between a casing and a casing support that secures the casing to
the wellhead stack assembly, the test plug tool providing a
fluid-tight seal with the casing beneath the joint between the
casing and the casing support.
[0014] By constructing test plugs of appropriate diameters, the
test plug tool may be used for testing the pressure integrity of a
variety of casing joints, including the joint between a surface
casing and a wellhead, the joint between an intermediate casing and
an intermediate casing mandrel, and the joint between a production
casing and a production casing mandrel.
[0015] Preferably, the test plug tool includes a test plug hanger
and a test plug, the test plug being positioned below the casing
joint.
[0016] Preferably, the test plug of the test plug tool comprises a
cup tool with flange supporting a gauge ring, a sealing element and
a cup for providing a fluid-tight seal between the test plug and
the casing.
[0017] The invention further provides a method for testing the
pressure integrity of seals and joints in a pressure control stack
mounted on a wellhead, together defining a wellhead stack assembly,
including testing the pressure integrity of a joint between a
casing and a casing support, the method comprising the steps of
inserting a test plug tool into the wellhead stack assembly with a
landing tool; landing the test plug in the casing beneath the joint
between the casing and the casing support; locking the test plug
tool in position; detaching the landing tool from the test plug
tool; retracting the landing tool from the wellhead stack assembly;
pressurizing the wellhead stack assembly to an estimated operating
pressure; and inspecting the seals and joints of the wellhead stack
assembly, including the joint between the casing and the casing
support, to ascertain that the seals and joints have withstood the
estimated operating pressure.
[0018] The method can be applied to the testing of various casing
joints, including the joint between a surface casing and a
wellhead, the joint between an intermediate casing and an
intermediate casing mandrel, and the joint between a production
casing and a production casing mandrel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Further features and advantages of the invention will become
apparent from the following detailed description, taken in
combination with the appended drawings, in which:
[0020] FIG. 1 is a cross-sectional view of a wellhead with a
control stack attached thereto and showing a test plug tool in
accordance with the invention with the test plug landed in the
surface casing beneath the joint between the surface casing and the
wellhead;
[0021] FIG. 1a is a cross-sectional view of the wellhead, control
stack and test plug tool shown in of FIG. 1, illustrating a landing
tool connected to the test plug tool for inserting the test plug
tool into the control stack and wellhead;
[0022] FIG. 2 is a cross-sectional view of a wellhead with a
control stack attached thereto and showing a test plug tool in
accordance with the invention with the test plug landed in the
intermediate casing beneath the joint between the intermediate
casing and the intermediate casing mandrel;
[0023] FIG. 3 is a cross-sectional view of a wellhead with a
control stack attached thereto and showing a test plug tool in
accordance with the invention with the test plug landed in the
production casing beneath the joint between the production casing
and the production casing mandrel;
[0024] FIG. 4 is a cross-sectional view of a wellhead with a
control stack attached thereto and showing a test plug tool
equipped with a backpressure valve in accordance with a further
embodiment of the invention;
[0025] FIG. 5 is a cross-sectional view of a wellhead with a
control stack attached thereto and showing a test plug tool
equipped with another embodiment of a backpressure valve in
accordance with the invention;
[0026] FIG. 6 is a cross-sectional view of the backpressure valve
shown in FIG. 5; and
[0027] FIG. 7 is a cross-sectional view of an upper portion of a
wellhead with a pressurized control stack attached thereto and
showing a test plug tool with a backpressure valve in accordance
with an embodiment of the invention.
[0028] It will be noted that throughout the appended drawings, like
features are identified by like reference numerals.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0029] In general, and as will be explained below, a test plug tool
can be used for testing the pressure integrity of a wellhead having
a pressure control stack mounted thereto. The wellhead and the
pressure control stack will be referred to hereinafter as a
"wellhead stack assembly". The test plug of the test plug tool is
designed to be landed below a casing joint formed between a casing
and a casing support so that this casing joint and all joints above
it in the pressure control stack can be pressure-tested. The
expression "casing joint" as used in this specification means a
joint between a casing and a casing support. A "casing", as persons
skilled in the art will understand, includes a surface casing, an
intermediate casing and a production casing. A "casing support"
means a component of the wellhead stack assembly that holds and/or
secures the casing to the wellhead stack assembly, and suspends the
casing in a well bore. Persons skilled in the art will understand
that where the casing is surface casing, the casing support is
typically a wellhead. Where the casing is an intermediate casing,
the casing support is generally an intermediate casing mandrel.
Where the casing is production casing, the casing support is
generally a production casing mandrel.
[0030] By constructing test plugs of suitable diameter, the test
plug tool can be used to pressure-test the surface casing, the
intermediate casing or the production casing. The test plug tool
includes a test plug hanger with fluid passages to permit test
fluids to pass therethrough, a test plug leg that extends
downwardly from the test plug hanger to support a test plug. In one
embodiment, the test plug is a cup tool that includes a cup sleeve
which terminates in a bullnose, the cup sleeve supports, above an
annular abutment, a gauge ring, an elastomeric sealing element and
an elastomeric cup. The gauge ring, sealing element and cup are
dimensioned to provide a high-pressure fluid seal against an inside
of the casing. During operation, the valves of the pressure control
stack are closed, the side ports are plugged and the stack is
pressurized to at least an estimated operating pressure to verify
that all seals and joints, including the casing joint, are able to
withstand the estimated operating pressure.
[0031] FIG. 1 illustrates what is known in the art as a pressure
control stack 10 [hereinafter the "stack"] which is configured for
pressure integrity testing. The expression "pressure integrity
testing" as used in this specification means a testing procedure
during which the stack is pressurized to at least an estimated
operating pressure and the joints and seals are inspected to verify
that they have withstood the test pressure.
[0032] At the base of the stack 10, and dug into the ground 12, is
a conductor 14. The conductor 14 is installed, or "stuffed", into a
"rat-hole" that is typically bored 60 to 80 feet deep, depending on
subsurface conditions. The conductor 14 supports a conductor ring
16 on the upper lip of the conductor. The conductor ring 16 is
beveled to form a bowl-shaped receptacle 18 for receiving a bottom
beveled portion of a wellhead 22. A surface casing 20 is connected
to the wellhead 22 below the side ports 24 of the wellhead. The
side ports 24 are sealed during pressure-testing.
[0033] The surface casing 20 is joined to the wellhead 22 at a
wellhead-to-casing joint 26. The wellhead-to-casing joint 26 is
formed between an upper portion of the surface casing 20 and a
lower portion of the wellhead 22, as illustrated in FIG. 1.
[0034] As shown in FIG. 1, mounted atop the wellhead 22 is a
drilling flange 30 which is secured to an upper portion of the
wellhead 22 by a wing nut 32. The drilling flange 30 has transverse
bores in a flanged portion 34 that house locking pins 36. Each
locking pin has a head 38. Mounted atop the drilling flange 30 is a
blowout preventer 40, well known in the art.
[0035] Before the stack is pressurized, a test plug tool 50 is
inserted into the bore of the stack 10. The test plug tool 50
includes a test plug hanger 51 and a test plug 53 which are
interconnected by a test plug leg 58.
[0036] The test plug hanger 51 of the test plug tool 50 includes a
landing joint connector, which is a box threaded socket 52 for
receiving one of a pin threaded landing joint 150 as illustrated in
FIG. 1a, a drill pipe, or a production tubing. In operation, the
drill pipe, the production tubing or the landing tool 150 is
threaded to the socket 52 and then the test plug tool 50 is lowered
into the stack 10 and the test plug is landed inside the casing, as
shown in FIG. 1a.
[0037] The test plug hanger 51 includes a hanger flange 54 that
extends laterally from the socket 52 to an outer radius of the test
plug hanger 51. The annular shoulder 54 has a beveled top edge that
is locked in place by the locking pins 36, so that the test plug
hanger 51 is restrained from upward movement. In addition, the
bottom surface of the hanger flange 54 rests on an annular abutment
31 in the drilling flange 30, which prevents the test plug hanger
51 from moving downwardly through the wellhead control stack. Since
the hanger flange 54 is locked between the annular abutment 31 and
the heads 38 of the locking pins 36, the test plug tool 50 cannot
be displaced during pressurization of the stack 10.
[0038] The hanger flange 54 also includes at least one fluid
passage 56 that are extends through the test plug hanger. During
pressurization of the stack, pressurized fluid flows through the
fluid passage 56. The fluid passage 56 thus permits pressure to
equalize on both sides of the hanger flange 54.
[0039] The test plug tool 50 has a test plug leg 58 integrally
formed with the hanger flange 54 and extending downwardly from the
underside of the hanger flange 54 to a test plug 53. A bottom end
59 of the test plug leg 58 is threaded to an upper end 61 of a cup
tool 60. The test plug leg 58 is preferably hollow to reduce a
weight of the test plug tool 50. As illustrated in FIG. 1, the cup
tool 60 includes a bullnose 60a at the bottom and a cup sleeve 60b
with an outer diameter less than that of the bullnose 60a. Because
the bullnose 60a has a greater outer diameter than that of the cup
sleeve 60b, the top surface of the bullnose 60a forms an annular
shoulder 60c. The annular shoulder 60c extends in the radial
direction but does not contact the surface casing 20. A small
annular gap 60d remains between the annular shoulder 60c and the
surface casing 20.
[0040] Supported directly above the annular shoulder 60c is a metal
gauge ring 62. The gauge ring 62 is dimensioned to support an
elastomeric sealing element 64 and to inhibit the elastomeric
sealing element 64 from extruding between the casing and the
bullnose 60c when the test plug tool 50 is exposed to elevated
fluid pressures. The elastomeric sealing element 64 forms a fluid
seal with the surface casing 20 when compressed by an elastomeric
cup 66 that is supported directly above the elastomeric sealing
element 64. The elastomeric cup 66 is preferably made of nitrile
rubber, although persons skilled in the art will appreciate that
other elastomers or polymers, such as polyethylene or polystyrene,
may also be used. The elastomeric cup 66 is also dimensioned to
form a fluid seal against the surface casing 20. The elastomeric
cup 66 is bonded to a steel ring that slides over the cup sleeve
60b. The steel ring includes a pair of radial grooves for seating
two O-rings 68. The O-rings 68 provide a fluid seal between the
elastomeric cup 66 and the cup sleeve 60b.
[0041] During pressure-testing, pressurized fluid flows through the
fluid passages 56 in the test plug hanger 51 to pressurize an
annular space 55. The annular space 55 is a generally annular
volume defined between the test plug leg 58 and the stack 10. The
annular space is pressurized to at least an estimated operating
pressure, which may be as high as 20,000 PSI (or about 140 MPa).
Since the cup 66 is below the wellhead-to-casing joint 26, this
joint is subjected to the test pressure. Thus, with the test plug
tool 50, it is possible to test the pressure integrity of the
wellhead-to-casing joint 26.
[0042] As illustrated in FIG. 2, the test plug 50 can be designed
and constructed with a smaller outer diameter for use in testing
the pressure integrity of a stack 10 configured with an
intermediate casing 70 in addition to the surface casing 20. As is
known by persons skilled in the art, industry regulations in
certain jurisdictions require that intermediate casing be run into
the well as a safety measure when exploiting a deep, high-pressure
well.
[0043] As shown in FIG. 2, the wellhead 22 is seated on the
bowl-shaped receptacle 18 of the conductor ring 16 which, in turn,
is mounted on the conductor 14. The surface casing 20 is joined to
the wellhead 22 below the side ports 24 at a wellhead-to-surface
casing joint 26. (These components are configured in the same way
as those shown in FIG. 1.)
[0044] The wellhead 22 supports an intermediate casing mandrel 72
which is threadedly fastened to the intermediate casing 70 to form
a joint with a frusta-conical interface which will be referred to
below as an intermediate casing-to-mandrel joint 75.
[0045] The drilling flange 30 is secured to an upper end 88 of an
intermediate head spool 80 by the wing nut 32. The drilling flange
30 includes lockdown pins 36 in the upper flanged portion 34. A
blowout preventer 40 is mounted to the upper flanged portion 34, as
described above.
[0046] The test plug tool 50 is inserted with a landing tool 150
(shown in FIG. 1a) which connects to the box threaded socket 52.
The test plug tool 50 is inserted into the stack 10 and positioned
at the location shown in FIG. 2, such that the test plug 53 is
beneath the intermediate casing-to-mandrel joint 75. The test plug
53 shown in FIG. 2 has a smaller outer diameter than the test plug
shown in FIG. 1. To ensure a fluid-tight seal, the cup tool 60, the
gauge ring 62, the sealing element 64 and the cup 66 are
constructed with diameters appropriate for the size and weight of
the intermediate casing, as is understood by persons skilled in the
art.
[0047] The test plug hanger 51 is secured in place by the locking
pins 36 in the upper flanged portion 34 of the drilling flange 30,
as already explained above. The heads 38 of the locking pins 36
engage the annular shoulder 54 of the test plug hanger 51 to
prevent the test plug from moving upward during pressurization. As
also explained above, the fluid passages 56 serve to equilibrate
pressure on each side of the test plug hanger 51 during
pressurization of the annular space 55.
[0048] As illustrated in FIG. 2, because the test plug tool 50 may
be inserted beneath the intermediate casing-to-mandrel joint 75,
this joint (and all the joints and seals above it in the stack) may
be pressure-tested to ensure that they are able to withstand at
least the estimated operating pressure.
[0049] FIG. 3 illustrates another embodiment of the test plug tool
50' which is designed to be used in testing the pressure integrity
of a production casing 90 which is run inside an intermediate
casing 70 for drop well production.
[0050] As illustrated, the test plug 53' of the test plug tool 50'
resembles the test plug 53 of the test plug tool 50 except that the
test plug 53' has a solid cup sleeve 60b', whereas the test plug 53
has tubular cup sleeve 60b. The reason for this design is explained
below. Other than the solid cup sleeve 60b', the test plug 53'
resembles the test plug 53 in that the cup tool 60' which supports
a metal gauge ring 62', a sealing element 64' and an elastomeric
cup 66', each of which have a smaller outer diameter than the outer
diameter of the test plug of FIG. 2, so as to fit the smaller bore
of the production casing 90. The test plug 50' also has O-rings 68'
to provide a fluid seal between a steel ring that supports the
elastomeric cup 60b of the cup tool 60.
[0051] The production casing 90 is fastened to a production casing
mandrel 92 to form a production casing-to-mandrel joint 95. A
flared bottom portion of the production casing mandrel 92 is seated
in a bowl-shaped portion 94 of the intermediate spool 80. The
intermediate spool 80 is secured to the wellhead 22 by a wing nut
32 as described above with reference to FIG. 2.
[0052] A tubing head spool 100 is mounted to a top of the
intermediate spool 80. The tubing head spool 100 includes flanged
side ports 114 and further includes a top flange 116 which has
transverse bores for housing locking pins 118 for securing a tubing
mandrel (commonly referred to as a tubing hanger or a "dognut"). A
flanged Bowen union 120 is mounted to a top of the top flange 116.
The flanged Bowen union 120 has a box threaded socket 124 for
receiving a pin threaded upper end 50a of the test plug tool 50.
The flanged Bowen union 120 also has a pair of annular grooves 125
for seating O-rings for providing a fluid-tight seal between the
upper end of the test plug and the flanged Bowen union 120. The
flanged Bowen union 120 has at its uppermost end a threaded union
126, a type of connection that is well know in the art for
connecting high-pressure lines, or the like. The flanged Bowen
union 120 includes an axial passage 127.
[0053] The test plug 50' has a differently shaped test plug hanger
51' than the test plug hanger 51 of the embodiment shown in FIGS. 1
and 2. The test plug hanger 51' shown in FIG. 3 includes a hanger
flange 54' with beveled shoulders dimensioned to fit snugly in the
bore of the tubing head spool 100. The lower beveled shoulder is
machined to rest against a bowl-shaped abutment in the tubing head
spool 100, which prevents the test plug 50' from descending further
into the wellhead stack assembly. Three peripheral grooves 57 are
machined into the hanger flange 54'. Three O-rings are seated in
the grooves 57 to provide a fluid-tight seal between the test plug
hanger 51' and the tubing head spool 100, because the tubing head
spool 100 above the tubing hanger bowl is normally not subjected to
elevated fluid pressure and the tubing head spool 100 is not
necessarily constructed to withstand high fluid pressures.
[0054] A fluid passage 58a is machined through a sidewall of the
test plug leg 58 to permit pressurized fluid to flow through the
central bore 127 of the flanged Bowen union 120, through the fluid
passage in the sidewall of the test plug hanger 51' and into the
annular space 55, i.e., the annulus between the test plug leg 58
and the wellhead stack assembly 10. Since pressurized fluid flows
below the production casing mandrel joint 95, this joint can be
pressure-tested.
[0055] In summary, the test plug tools 50, 50' shown in FIGS. 1, 2
and 3 may be dimensioned for use in testing the pressure integrity
of pressure control stacks attached to wellheads. As described and
illustrated above, the test plug tools may be used to test the
pressure integrity of the wellhead-to-surface casing joint (FIG.
1), the intermediate casing mandrel joint (FIG. 2), and the
production casing mandrel joint (FIG. 3). In each of these three
applications, the test plug tool is also useful for testing the
various joints and seals above the wellhead surface casing joint,
the intermediate casing mandrel joint, or the production casing
mandrel joint, as the case may be, including the rams of blowout
preventer(s) located above the wellhead stacks, and any control
valves mounted to the wellhead stack 10.
[0056] As shown in FIG. 4, the test plug tool 50 may further
include a backpressure valve 200 which communicates with an axial
passageway 220 in the test plug hanger 51. The backpressure valve
is a one-way valve used to ensure that a fluid-tight seal is
provided by the test plug tool. If the test plug tool fails to
provide a fluid-tight seal, pressurized fluid can leak past the
test plug 53, causing backpressure to build up downhole of the test
plug tool. Such downhole backpressure may damage the casing or
cause other problems.
[0057] As shown in FIG. 4, the backpressure valve 200 is a
generally annular body 202 with pin threads for engaging a box
thread in a test plug hanger 51. The backpressure valve 200 also
has a spring-loaded ball valve, which includes a ball 216 that is
forced downwardly against an annular shoulder by a spring 218. The
spring is retained by an annular retainer cap 224 that threads onto
the annular body 202. The structure of the backpressure valve will
be described in greater detail below with regard to FIG. 6. In
operation, if the test plug tool leaks and backpressure builds up
beneath the test plug 53, pressurized fluid will travel up a
central bore 50b of the test plug tool 50 and up the axial
passageway 220. If the backpressure is more than a few pounds per
square inch (PSI), the spring-loaded ball valve will be displaced
upwardly against the spring, thereby permitting pressurized fluid
to flow up a central bore of the landing tool 150, thereby alerting
an operator of the leak.
[0058] FIG. 5 illustrates another embodiment in which the test plug
tool 50 employs another embodiment of a backpressure valve 200, the
structure of which is illustrated in greater detail in FIG. 6. The
backpressure valve 200 shown in FIG. 6 also has a spring-loaded
ball valve which is displaced upwardly when the backpressure
exceeds the compressive resistance of the spring.
[0059] As shown in FIG. 6, the backpressure valve 200 includes a
generally annular body 202 which has threads 203 for connecting to
an annular anchor that in turn threadedly engages (via threads 208)
to the test plug hanger 51. A gasket 210 sits in an annular groove
to provide a fluid-tight seal between the test plug hanger 51 and a
lower portion 206 of the annular anchor 204.
[0060] The backpressure valve includes a ball 216 which is forced
downwardly by a compression spring 218 against an annular gasket
214 which sits on annular shoulder of the anchor 204. The annular
shoulder defines an aperture through which pressurized fluid may
flow. In other words, the backpressure valve is a one-way
spring-loaded ball valve in which the spring exerts a downward
force on the ball for obstructing the aperture defined by the
annular shoulder.
[0061] In operation, if a leak occurs and the backpressure exceeds
the compressive resistance of the spring, then the ball is
displaced upwardly, thereby permitting pressurized fluid to flow
from the axial passageway 220 to an upper passageway 222 and
upwards through a central bore 151 of the landing tool 150.
[0062] Depicted in FIG. 7 is a set-up for pressurizing the wellhead
and control stack. The test plug tool 50 is inserted into the stack
using the landing tool 150 and is locked into place by locking pins
36 in the drilling flange 30. Mounted atop the drilling flange 30
is the blowout preventer 40. Secured atop the blowout preventer 40
is the tubing head spool 100 having flanged side ports 102 for
injection of pressurized fluids for testing the pressure integrity
of the wellhead and stack. Secured atop the tubing head spool 100
is a tubing adapter 250. The tubing adapter 250 is flanged to the
tubing head spool and is sealed thereto with a ring gasket which is
housed in an annular groove 252. The tubing adapter 250 has threads
255 for connection to a retainer nut 260. The tubing adapter also
has a radially inward annular cavity known as a stuffing box. The
stuffing box houses a packing retainer ring 262, a chevron packing
264 and a packing nut 266. Accordingly, with the stack configured
as shown in FIG. 7, the annular space 55 can be pressurized to test
the pressure integrity of the wellhead and stack. If pressurized
fluid leaks past the test plug, backpressure will force open the
backpressure valve 200, thereby permitting fluid to flow up the
central bore 151 of the landing tool 150.
[0063] Persons skilled in the art will appreciate that these test
plug tools may be modified to suit similar pressure-testing
applications. The embodiments of the invention described above are
therefore intended to be exemplary only. The scope of the invention
is intended to be limited solely by the scope of the appended
claims.
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